The present invention relates generally to a hydraulic shock absorber with a vortex valve therein. More specifically, the invention relates to a shock absorber capable of effectively preventing the shock absorber from producing excessive absorbing force.
A shock absorber having a vortex chamber in the piston thereof for producing an absorbing force against a shock applied thereto is well known. Typical construction of such shock absorber has been disclosed in the U.S. Pat. No. 3,362,508 to Mayer. In the U.S. Pat. No. 3,362,508, there is illustrated a shock absorber having a piston in sliding engagement with a cylinder, dividing the cylinder into first and second chambers. A vortex chamber is mounted on the piston with an axial passageway for communication with the first chamber, tangential and radial passageways for communication with the second chamber, and a member with an opening which is movable with respect to the piston to vary the restriction of the radial and axial passageways. A similar vortex valve shock absorber has also been disclosed in the U.S. Pat. No. 3,672,474 to Mayer et al. In the U.S. Pat. No. 3,672,474, there is disclosed a shock absorber, which produces a flowrate tailored to fit a pressure difference relationship, including a laminar flow device and an orifice restriction connected to a radial-and-tangential inlet of a vortex valve, with both connected in parallel to the upstream pressure source. Flow across the assemblage will be such that the vortex valve will act like a smaller orifice at lower flows and a large orifice at high flows, or vice versa, due to the shifting of the respective shares of the total flow accommodated by the laminar flow device and the orifice restriction. This arrangement is incorporated into a shock absorber to produce improved output damping characteristics.
U.S. Pat. No. 3,672,474 has a means for relieving the excessive fluid pressure in the vortex chamber. The relieving means comprises a plurality of radially-extending multiconduit fluid passages. The fluid passages permit fluid flow therethrough regulated by the fluid pressure in the vortex chamber. Although this will be effective for relieving excessive fluid pressure when the piston stroke becomes larger than a predetermined value or the piston speed becomes higher than a predetermined value, it will also reduce the absorbing force produced by the vortex when the piston stroke is smaller than the predetermined value or the piston speed is lower than the predetermined value.
Another typical conventional construction of the pressure-relieving means for excessive fluid pressure produced by the vortex in the vortex chamber comprises a fluid passage formed in the piston and a resilient closure member provided for closing one end of the fluid passage in response to a set pressure given to the resilient closure member. According to this construction, the fluid pressure in the vortex chamber can be prevented from increasing excessively.
The present invention is to improve the conventional construction of the shock absorber with a resilient closure member in order to provide improved shock absorbing characteristics.